The OpenAL Installer for Windows will install the OpenAL 1.1 libraries, enabling support for core OpenAL operations as well as extensions such as EAX and EFX. The installer supports both 32-bit and 64-bit versions of Windows.

Go to Documents\BioWare\Mass Effect\Config\BioEngine.ini. Find: [ISACTAudio.ISACTAudioDevice]. It most likely now reads this:

[ISACTAudio.ISACTAudioDevice]MaxChannels=64 <--if you have an X-Fi, change this to 128; Audigy stay with 64TimeBetweenHWUpdates=15MinOggVorbisDurationGame=20MinOggVorbisDurationEditor=4TotalAvailableChannels=62 <--if you have an X-Fi, change this to 128; Audigy change to 64DeviceName=Generic Hardware <--just let this be, or make empty doesn't matter

Leave the rest. Save and Exit.

Launch game and enjoy.

You can check in Documents\BioWare\Mass Effect\Logs\MassEffect.log that your X-Fi (or Audigy) was called to work.